<template>
<div>
  <input type="text" placeholder="Input Underline">
  <span></span>
</div>
</template>

<style scoped>
div {
  position: relative;
}

input {
  width: 6.5em;
  color: white;
  font-size: inherit;
  font-family: inherit;
  background-color: transparent;
  border: 1px solid transparent;
  border-bottom-color: hsla(185, 100%, 62%, 0.2);
}

input:focus {
  outline: none;
}

input::placeholder {
  color: hsla(0, 0%, 100%, 0.6);
}

span {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 1px;
  background-color: #3cefff;
  transform-origin: bottom right;
  transform: scaleX(0);
  transition: transform 0.5s ease;
}

input:focus ~ span {
  transform-origin: bottom left;
  transform: scaleX(1);
}
</style>

